Mils vs MOA, By Caylen Wojcik

I get asked for my thoughts on this so-called debate all the time, and it most often comes from hunters looking to understand what a milliradian is, and why the military and practical rifle competitors prefer it over the minute of angle or MOA. For hunters, this is a completely foreign concept, especially considering that minutes of angle (and its counterpart, inches per hundred yards) were the only accepted units of measure for optics and rifle accuracy up until around the year 2005-2006.

The hard truth? There’s not much difference really. Both are angular units of measure, and both will get you what you need in the end, which is a bullet placed where you want it to go. There are a lot of misconceptions surrounding the topic, and as a result, “spirited” discussions are not uncommon. In this article, we’ll unpack the pros and cons of both so you can decide which is best for your scoped rifle application.

Even with the advent of milliradians and its popularity amongst the military and practical rifle competition community, we still commonly use minutes of angle to quantify a rifle’s accuracy. For those die-hard minute of angle users, not to worry, the minute of angle isn’t going anywhere anytime soon. I think it’s best to start this discussion with where these angular units of measure came from, and the history of their use.

Minutes of Angle or MOA are derived from the angular division of a circle. Most people associate this measurement with a compass rose. This unit of measurement is actually man-made, meaning it was derived as a result of a need, not a mathematical function. Its original use was for plotting locations on the surface of the earth, as well as astronomy, and plotting the trajectory angles for early era artillery fire. The MOA eventually found its way into shooting, and measuring extremely small angles to compensate for the effects of gravity, drag, and wind deflection on a projectile in flight.

There are 360 equal parts inside of a circle, which are called degrees. Each degree can be further broken down into 60 equal segments, which are minutes of angle. Each minute of angle can be further broken down into 60 seconds of angle. What this means to us as shooters is that one minute of angle equals 1.047 inches of linear measurement between the two rays of the angle at a distance of 100 yards. This is a linear measurement, and the distance between the two rays will increase proportionally the farther from the origin of the angle, meaning at 500 yards one MOA equals 5.235 inches, and at 1000 yards, one MOA equals 10.47 inches. There are 21,600 minutes of angle per circle, and with most modern rifle scopes offering 1/4 MOA adjustments, we have the ability to make very precise adjustments, which alter the point of impact of our bullets on the target.

What we just discussed would be classified as True MOA. Some riflescopes are calibrated for Shooter’s MOA which is a rounded number, down from a True MOA. A Shooter’s MOA equals 1” at 100 yards, 5” at 500 yards, and 10” at 1000 yards. It’s critical that you know what your riflescope is calibrated to. If you’re using elevation and windage data that is True MOA, and your scope is calibrated for Shooter’s MOA, you’ll have a significant variation as the distance to the target grows.

The other angular unit of measure that has increased in popularity in the shooting sports is the milliradian. Commonly referred to as the metric angular unit of measure, the milliradian works in units of 10’s. Also known as “mils”, and contrary to the MOA, this measurement is a mathematical function, derived from trigonometry and the mathematical constant of Pi. You still with me?

Radians are commonly used in engineering and manufacturing. The mil has been used for quite some time in the world of artillery and naval gunfire, as using the mil on a compass rose offers a much higher resolution for angular direction than a degree does — more on that later. So, without getting too deep into the weeds on the mathematical side of things, a milliradian is 1/1000th of a radian. According to the law of radians, radius = arc length, meaning that the length of the radius will take up that same distance covering a part of a circle’s circumference. 2 x π = R. So, 2 x 3.14159 = 6.2831 radians per circle. We want to get to milliradians, so using the metric system, all we have to do is move the decimal three places to the right, giving us approximately 6,283 mils per circle.

Milliradian based rifle scopes are calibrated for 1/10th of a mil per increment. What this means to us is that 1 mil equals 3.6” of linear measurement between the two rays of the angle at 100 yards away. The same holds true for mils as it does for MOA in that the linear distance between the two rays of the angle grow proportionally with the distance from the origin of the angle. At 500 yards, 1 mil equals 18”, and at 1000 yards 1 mil equals 36”. Being that a mil based scope is calibrated for 1/10th increments, each 10th of a mil equals .36” at 100 yards, or 3.6” at 1000 yards. I’m sure you can see that mils don’t get us the same resolution as a minute of angle does, but there are significant benefits to using mils over MOA.

Now that we understand what both of these angular units of measure represent, we can decide which works best for your application. I’ll say that people really get wrapped around the axle with this, and it’s completely unnecessary. The common pitfall I see shooters get themselves into is that they constantly try and convert the unit of measure to an inch value. Look, I get it, we Americans measure stuff in inches and it’s how our brains are programmed to work, but trying to convert either an MOA or a mil to inches is a complete waste of brain power. STOP thinking in inches, and start thinking in the angular unit of measure you have in your optic! That’s all you need!

Most modern rifle scopes are equipped with a reticle that will be calibrated in the same unit of measure as your turrets. If that’s not the case, I’d be questioning your purchase and considering buying an optic where you’re comparing apples to apples, or oranges to oranges. Anything different is a huge hassle. I know, because that’s how I was brought up in the community. I had an MOA turret and a mil based reticle. This is where the famed “sniper math” came from and all that term was referring to was the conversion from MOA to mils, or vice versa. I’m not even going to get into that, or how to do it because I don’t have the space to do so within the constraints of this article. And, besides, it’s a waste of time now.

If your scope’s reticle is placed in the first focal plane, your reticle is essentially a tape measure in whatever angular unit of measure it’s calibrated to. If you have a reticle in the second focal plane, then your reticle is still a tape measure, but it’s only going to be the correct measurement at a specific magnification. Consult your scope’s manual to find out what that magnification setting is if you don’t know. If your scope’s reticle is a BDC based system with some arbitrary dimension between the markings, consider buying a new scope. Having your reticle speak the same language as your turrets will help you make more precise wind corrections, and you’ll have considerably more precise second shot corrections should you miss.

My preferred unit of measure to work in is mils, the only reason being that the total numerical value of a mil come-up vs an MOA come-up is a far smaller number, and it’s easier to comprehend. Those smaller numbers mean it’s easier for me to remember my come-ups every 100 yards in the event I lose my data, and those smaller numbers mean my windage calculations and corrections are easier to manage in my head when I’m doing things on the fly.

As an example below, I’ll give some numbers for a 6.5mm Creedmoor firing a 140-grain ELDM at 2800 fps, at a target at 1000 yards with a 10 mph full-value wind. Take a look and see what you think would be easier for you to comprehend and remember.

 

1000 Yard Elevation
10 MPH F.V. Wind

MOA

Come-up: 30.7

Windage: 6.9

Mils

Come-up: 8.9

Windage: 2.0

 

What you choose is totally up to you, and it’s really all about how your brain works. I remember when the Marine Corps got the first Schmidt & Bender PMII’s. I was transitioning out of the Corps, and when I saw the scope was calibrated in mils, I knew that the community was in for some growing pains. It was a struggle for some time, as everyone was trying to convert those mils to MOA instead of just simply abandoning MOA for mils. Another reason I prefer to use mils is that there are a couple really handy and hasty wind and elevation calculation formulas that a shooter can do in their head using simple math if there’s no time to take a look at your data. That’s important for folks who use their rifle in high-stress situations such as hunting, or combat. Those hasty formulas don’t work with MOA because the overall numbers in MOA are too large and the math doesn’t work out.

In closing, I’ll reiterate what I stated above; it truly doesn’t matter what you choose to use. As long as what you choose for your angular unit of measure makes sense to you and you can comprehend it under stress, it does not matter. I’ll caveat that by saying if you’re using mils and your hunting partner is still thinking in inches and trying to convert that to MOA, and then to mils, you’re going to be in for some heated discussions on the range. Make sure everyone is talking the same language, and STOP trying to convert those angular units of measure to inches. It’ll make life easier for everyone, and you’ll be far more effective while you’re on the range or in the field.

Posted by Adam Janke